What is AZW3?

AZW3 (also called KF8) is Amazon's modern eBook format that replaced the older MOBI/AZW formats. It supports advanced features like embedded fonts, fixed layouts, rich media, and precise formatting using HTML5 and CSS3. AZW3 files can include DRM protection and are optimized for Kindle devices and apps.

The format combines the best of EPUB features with Amazon's ecosystem integration. AZW3 books sync across devices, support Whispersync for Voice, X-Ray features, and enhanced typesetting. While proprietary to Amazon, AZW3 has become one of the most popular eBook formats due to Kindle's market dominance.

Did you know? AZW3 can embed fonts for consistent reading across all devices!

History

Amazon developed KF8 to modernize their eBook platform and compete with EPUB's advanced features while maintaining compatibility with the Kindle ecosystem.

Key Milestones

  • 2007: Original AZW format (MOBI-based)
  • 2011: KF8 (AZW3) introduced
  • 2013: Kindle Fire HDX launches with KF8
  • 2015: Enhanced Typesetting added
  • 2019: Print Replica support
  • Present: Standard Kindle format

Key Features

Core Capabilities

  • HTML5/CSS3: Modern web standards
  • Embedded Fonts: Custom typography
  • Fixed Layouts: Children's books, comics
  • Rich Media: Audio, video support
  • Enhanced Features: X-Ray, Word Wise
  • Whispersync: Cross-device sync

Common Use Cases

eBooks

Novels, non-fiction

Textbooks

Educational content

Children's Books

Fixed-layout content

Magazines

Rich media publications

Advantages

  • Advanced typography and formatting
  • Kindle ecosystem integration
  • Enhanced reading features
  • Fixed-layout support
  • Cross-device syncing
  • Better than older MOBI
  • Rich media capabilities

Disadvantages

  • Proprietary Amazon format
  • DRM-locked to Kindle devices
  • Not compatible with non-Kindle readers
  • Requires conversion for other platforms
  • Less universal than EPUB

Technical Information

Format Specifications

Specification Details
File Extension .azw3, .kfx
MIME Type application/vnd.amazon.ebook
Format Type eBook
Based On HTML5, CSS3
DRM Optional (Amazon DRM)
Compression Yes

Common Tools

  • Readers: Kindle devices, Kindle app (iOS/Android/PC)
  • Creation: Kindle Create, Kindle Previewer
  • Conversion: Calibre, Kindle Previewer
  • Management: Send to Kindle